Unused JavaScript bytes and the Core Web Vitals

Sites with 400 to 850 KB of unused JS unused JavaScript bytes have a good INP most often: 100%, against 99% of all sites. Sites with over 1.5 MB of unused JS unused JS have it least often, at 98%.

Sites with 400 to 850 KB of unused JS unused JavaScript bytes have a good LCP most often: 90%, against 86% of all sites. Sites with over 1.5 MB of unused JS unused JS have it least often, at 81%.

400 to 850 KB of unused JS is the most used: 26.9% of sites.

On WordPress, 31% of sites use 850 KB to 1.5 MB of unused JS unused JavaScript bytes, and 100% of WordPress sites have a good INP, against 99% of all sites. On Shopify, 64% of sites use over 1.5 MB of unused JS, and 99% of Shopify sites have a good INP.

On WordPress, 31% of sites use 850 KB to 1.5 MB of unused JS unused JavaScript bytes, and 76% of WordPress sites have a good LCP, against 86% of all sites. On Shopify, 64% of sites use over 1.5 MB of unused JS, and 97% of Shopify sites have a good LCP.

PlatformUnused JavaScript bytes on its sitesGood INP

Sites with unused JavaScript bytes 206,167 sites400 to 850 KB unused 27%Over 1.5 MB unused 26%850 KB to 1.5 MB unused 25%Under 400 KB unused 22%99%

Adobe Commerce 1,095 sitesOver 1.5 MB unused 73%850 KB to 1.5 MB unused 21%100%

Wix 5,825 sitesOver 1.5 MB unused 72%850 KB to 1.5 MB unused 28%100%

Squarespace 2,258 sitesOver 1.5 MB unused 100%100%

Joomla 2,550 sitesUnder 400 KB unused 49%400 to 850 KB unused 36%850 KB to 1.5 MB unused 12%100%

Drupal 3,295 sites400 to 850 KB unused 40%850 KB to 1.5 MB unused 26%Under 400 KB unused 19%Over 1.5 MB unused 15%100%

WordPress 65,496 sites850 KB to 1.5 MB unused 31%400 to 850 KB unused 30%Over 1.5 MB unused 23%Under 400 KB unused 16%100%

Shopify 8,572 sitesOver 1.5 MB unused 64%850 KB to 1.5 MB unused 23%400 to 850 KB unused 13%99%

400 to 850 KB unused Over 1.5 MB unused 850 KB to 1.5 MB unused Under 400 KB unused

Does the platform explain the unused JavaScript bytes difference?

On WordPress, 100% of sites with 400 to 850 KB of unused JS unused JavaScript bytes have a good INP, against 99% of WordPress sites with over 1.5 MB of unused JS. Within WordPress, sites with 400 to 850 KB of unused JS and over 1.5 MB of unused JS have a good INP about equally often. On Shopify, 100% of sites with 400 to 850 KB of unused JS unused JavaScript bytes have a good INP, against 99% of Shopify sites with over 1.5 MB of unused JS. Within Shopify, sites with 400 to 850 KB of unused JS and over 1.5 MB of unused JS have a good INP about equally often.

On WordPress, 82% of sites with 400 to 850 KB of unused JS unused JavaScript bytes have a good LCP, against 68% of WordPress sites with over 1.5 MB of unused JS. Within WordPress, sites with 400 to 850 KB of unused JS have a good LCP more often. On Shopify, 98% of sites with 400 to 850 KB of unused JS unused JavaScript bytes have a good LCP, against 96% of Shopify sites with over 1.5 MB of unused JS. Within Shopify, sites with 400 to 850 KB of unused JS and over 1.5 MB of unused JS have a good LCP about equally often.

How dead JavaScript code still blocks the main thread

The browser cannot skip parsing or compiling unused functions inside a downloaded bundle. Across 55,440 sites (26.9%) with 400 to 850 KB of unused JS, 100% pass field INP at an 45ms median, while the 25.9% (53,454) exceeding 1.5 MB of unused JS drop to 98% good INP (60ms median).